En dash: Twice as long as a hyphen, the en dash is a symbol (--) that is used in writing or printing to indicate a range, connections or differentiations, such as 1880-1945 or Princeton-New York trains.
Em dash: Longer than the en dash, the em dash can be used in place of a comma, parenthesis, or colon to enhance readability or emphasize the conclusion of a sentence. For example, She gave him her answer --- No!